NLR Reports Repository

Brugman, J.

Nationaal Lucht- en Ruimtevaartlaboratorium
National Aerospace Laborator y NLR
NLR TP 96520
Video for flight test
J. Brugman
217-02
DOCUMENT CONTROL SHEET
                     
ORIGINATOR'S REF.                    SECURITY CLASS.
                     NLR TP 96520 U                 Unclassified
ORIGINATOR 
National Aerospace Laboratory NLR, Amsterdam, The Netherlands
TITLE  
Video for flight test
PRESENTED AT
The 8th European Symposium of the Society of Flight Test Engineers at
Blackpool, England, June 10, 1996.
AUTHORS                 DATE                 pp    ref
J. Brugman
                  
960912 10 0
DESCRIPTORS   
Airborne equipment Flight test vehicles
Aircraft equipment Image processing
Data recorders Trajectory measurement
Equipment specifications Video equipment
ABSTRACT
The NLR is using video systems for flight test since 1984. The systems
used formerly consisted of black and white tube camera's and U-matic
video recorders with 2 hour tapes. Nowadays miniature colour remote head
camera's are used in combination with time/text annotation and mixing
capability, HI-8 video recorders with up to 3 hours endurance and high
resolution monitors. The systems consists of max 4 video channels. All
the functions can be controlled remotely by a serial RS422 link. Because
it was decided that the ultilisation of airborne video equipment was not
essential, the choice in devices was broad, and the hardware costs could
be kept low. Nevertheless final tests proved that the system withstands
the DO-160 environmental conditions. The NLR has recently introduced a
second generation Image Processing System, which is capable to digitise
and store real time sequences of half an hour. Subsequently it is
possible to submit these images to automatic measurements, which for
instance enables the accurate calculation of trajectories of aircraft or
other objects. The image processing will be introduced and an example of
the data processing will be given. This system has been developped under
a contract awarded by the Netherlands Agency for Aerospace Programs
(NIVR) for use in Fokker flight programs.
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TP 96520
Contents
Abstract 5
Nomenclature 5
1. Introduction and applications 6
2. overview of the system, block diagram 6
3. The camera 7
4. The recorder 7
5. The VCU 8
6. The monitor 9
7. The Image Processing system 10
8. Examples of applications 10
9. Conclusions 11
(11 pages in total)
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TP 96520
This page is intentionally left blank
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TP 96520
ABSTRACT
The NLR is using video systems for
flight test since 1984. The systems used
formerly consisted of black and white
tube camera’s,  and U-Matic video
recorders with 1/2 hour tapes.
Nowadays miniature colour remote head
camera’s are used in combination with
time/text annotation and mixing
capability, HI-8 video recorders with up
to 3 hours endurance and high resolution
monitors. The systems consist of max 4
video channels. All the functions can be
controlled remotely by a serial RS422
link.
Because it was decided that the utilisation
of airborne video equipment was not es-
sential, the choice in devices was broad,
and the hardware costs could be kept low.
Nevertheless final tests proved that the
system withstands the DO-160 environ-
mental conditions.
The NLR has recently introduced a
second generation Image Processing
System, which is capable to digitise and
store real time sequences of half an hour.
Subsequently it is possible to submit
these images to automatic measurements,
which for instance enables the accurate
calculation of trajectories of aircraft or
other objects. The image processing
system will be introduced and an example
of the data processing will be given.
This system has been developped under a
contract awarded by the Netherlands
Agency for Aerospace Programs (NIVR)
for use in Fokker flight test programs.
NOMENCLATURE
ASCII International standard for
text.
EMI Electro Magnetic
Interference.
EEPROM Electrical Erasable              
                     Programmable Read Only   
                       Memory
IRIG-B Inter Range
Instrumentation Group
timecode standard
JPEG Joint Photographers Expert
Group=Standard for image
compression.
NLR National Aerospace
Laboratory
RS422/RS232 Standards for serial 
Datatransmission.
VCU Video Control Unit.
Y/C Video signal connection
consisting of separate
luminance and
chrominance signals
VIDEO FOR FLIGHT TEST
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TP 96520
1. Introduction and applications.
The applications for video for flight test
are emerging. Recent test aircraft carry
up to 15 possible camera positions where
4 are used at the same time, with 4
recorders and 4 monitors.
All pictures are annotated with time
of day, and some parameters in
engineering units.
The images are frequently used for
measurements, both for aircraft
positioning and object movements. For
this application a digital image storage
and processing system is used.
Examples of video applications are:
Inside the aeroplane:
- crew: ergonomics, cockpit workload.
- instruments: reading.
Outside the aeroplane:
- icing.
- flow investigation: tufts, smoke.
- water ingestion.
- landing gear.
- separations.
- lowering of static bomb or cone.
- engine: inlet and exhaust; ice- and smo-
ke.
- control surfaces.
- wings.
- propellers.
- tail.
- positioning.
2. Overview of the system.
The system consist of up to 4 complete
video systems, uses miniature remote
head camera's, Hi-8 video recorders, cen-
tral switching and annotation unit of own
development, and 9" or 14" video
CAMERA 1...4 CAMERA ELECTRONICS
VCU
REC 2
MONITORS
IRIG-B
TIME
CONTROL
BLOCKDIAGRAM VIDEO SYSTEM
REC 1 REC 4REC 3
audio
POWER
sync
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TP 96520
monitors. Remote Control is accomplished
via an RS422 link from an Instrument
Control Computer or a PC. Remote control
is also possible via simple Recording
on/off switches in the cockpit. The
cameras feature shutters for short exposure
times to image moving objects sharply and
to automatically correct varying lighting.
By mixing it is possible to compose one
picture out of two cameras.
Time lapse recording is available for long
duration recordings of up to 1 week.
The data processing equipment consist of a
frame grabber, a real time hardware JPEG
ompressing system and 2 fast hard disk for
storage. The storage capacity is 30 minutes
of life video in total. The quality is of high
level, exceeding HI-8 standard. Inputs are
available for composite video, Y/C and
Component. The Image Processing
software is able to perform corrections on
the recorded images and to measure
objects in the images with sub pixel
accuracy.
3. The camera.
The camera is a commercially available
remote head camera with the following
features:
- Remote head of 16 mm diameter, 100     
   mm long.
- Head/Electronics Cables up to 30 meters.
- Shutter from 1/50 to 1/10.000 sec.
- Auto shutter option for automatic lighting
   correction.
- High resolution of 752 x 582 pixels.
- Y/C output for sharp pictures.
- relatively low cost.
- Objectives of  4,  7.5,  15 and 24 mm.
The shutter has an option to adapt for
variable lighting. This is a very useful
function in the varying lighting conditions
in flight. The camera is modified to allow
for remote control of the shutter functions
to be able to correct remotely for backlight
situations if necessary. The camera is
tested for Temperature, Altitude, Vibration
and EMI. The results are very good, only
for EMI some additional filtering was ap-
plied. The camera head functions good up
to -75 deg C (limit of test equipment!).
The automatic shutter option proved to be
very useful in flight conditions because the
light varies constantly depending on flight
direction and sunlight. A dripwatertight
housing is developed for outside
applications of the camera, with a simple
heater to prevent condensing of the lens
when the aircraft is descending.
The camera cable is a special 12 wire cable
with dedicated connectors. These cables
are fabricated in house. In dry weather the
camera is used outside without housing.
Power requirement is 12 VDC at 0.7 A.
Special tray's are designed to mount the
camera electronics unit in the
instrumentation racks.
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TP 96520
4. The recorder.
The recorders used are the V80AB-F,
Milspec airborne HI-8 recorders from
TEAC.
The HI-8 system has an endurance of 90
minutes per tape, 3 hours in long play
mode. The HI-8 system is commercially
and professionally widely used, so there
is a broad choice in replay equipment.
The recorders are compact and rugged
and completely remote controllable with
RS 422 serial signals. Remote control via
discrete on/off signals is also possible.
The recorder is tested for Temperature,
Altitude, Vibration and EMI with good
results. For low temperatures internal
heaters are used. The recorder is modified
by adding a counter for running hours, to
be able to plan the periodic maintenance,
and a remote/local switch. 
In other applications these recorders are
used for data recording in combination
with Merlin encoders.
The Time Lapse option permits the
recording of 0.5 sec video every 10, 20 or
60 seconds, resulting in recording time of
30, 60 or 180 hours (1 week). This is a
very useful function for the recording of
intermittent troubles with icing or
troublesome mechanisms.
5. The VCU.
The Video Control Unit is the central
device in the video system. The functions
of the VCU are:
1. 12 VDC Power supply of the cameras
2. 4 discrete signals for shuttercontrol of
the cameras
3. Mixer for the camera video signals. The
VCU is able to combine two video
signals into one over an arbitrary cut-
out. This function is controlled by a
command like:
@ (rec no)(cam no)(x,y position start of
cut)(x,y position end of cut) (CR)
4. Input selector for the recorders. Each
camera can be hooked up to each of the
recorders.
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TP 96520
5. Receiver and decoder of the Time
Code. The IRIG -B timecode signal is
decoded and annotated as one line of
text to the four recorder signals as:
123  10:55:59:999
Format: Record number  
hours:minutes:seconds:millseconds.
If the IRIG-B fails, the VCU will
continue on its own clock while 
displaying ???  for the record number.
6. Receiver for RS422/RS232 control
signals and Annotator text. This is the
connection which is used for remote
control of the entire video system.
7. Annotator for the 4 video recorders.
The ASCII text that is coming in via
RS422 is coded with recorder 1 to 4;
and annotated as a 38 character line of
text in the image of the selected
recorder. The text can be selected big
or small, at the top or bottom of the
image, transparent or with
background. Text without recorder
number is routed to all four
annotators.
8. Distributor of RS422 control signals to
the recorders. The control signals
coded for recorder 1 to 4 are sent to
the appropriate recorder. The status
signals of the recorders (inclusive tape
counters) are sent back on request.
9. Input selector for the 4 monitors.
Every monitor can be switched
directly to each camera- or recorder
output.
10. Distributor of audio record and replay
signals. The communication system in
the aeroplane is connected to the
recorder inputs, the recorder outputs
being connected to the monitor
loudspeakers.
The VCU is developed by the NLR
electronics department, and tested for
Temperature, Altitude, Vibration and EMI.
It uses 115 VAC 400 Hz 80 W, and for the
videorecorders 28 VDC. The VCU status
is stored in EEPROM to make it robust
against short and long power interrupts.
The VCU works with Y/C (separated
Luminance and Chrominance) circuits
througout the whole device to give sharp
images, and preventing cross colour
effects.
6. The monitor
The monitors are professional  high
resolution Sony 9” and 14” monitors.
They are modified to withstand EMI and
vibration tests. Special windows are placed
in front of the picturetubes to protect the
viewer from implosion of the tube and to
reduce EMI penetrating through the
screen. The Power supplies are modified
for 115 VAC 400Hz. Special racks are
designed for stable mounting. For power
and video ruggedised connectors are
applied.
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TP 96520
7. The Image Processing system.
For the processing and measuring of video
images an Image Capture and Processing
system is available. The capture system
consists of a real time colour frame
grabber with built in timebase corrector,
real time colour JPEG video compressor
and fast hard disks. The complete system is
housed in a Pentium PC.  The resolution is
752 x 576 pixels, there is room for half an
hour full quality video on the harddisks.
After the capture each frame is digital
accessible, and there is a very convenient
search capability. In this way you can
select the pictures you want to process
easily.
Besides this the image processing system
offers the following features.
1. Picture enhancement when the lighting
is not optimal. This process will remove
shading effects
2. Automatic selection of objects on the
base of a predefined shape.
3. Automatic measurement of the position,
area, perimeter, etc. of the object in sub
pixel accuracy.
4. Export of the measured data in any
form.
8. Examples of applications:
Checking of the accuracy of a radio
altimeter.
The aeroplane is marked with circles at the
wingtips at known distance. Flying over a
vertical upwards looking video camera,
pictures are taken with short exposure
times. No instrumentation in the aeroplane
is needed.
The circles in the pictures are measured,
and from this the altitude of the aircraft
can be calculated. Accuracy can be better
than 0.2 %.
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TP 96520
Wingtorsion measurement.
The videocamera is installed behind a
window over the wing. The wingtip is
marked with black and white stripes.
During  flight tests the images are
recorded. Using the Image Processing
system the deflection and torsion of the
wingtip is measured to an accuracy of 
1 mm and 0.05 deg.
Aircraft Positioning.
This method is used for navigation system
reference measurements. The aircraft is
flying over a runway with a downlooking
camera viewing the runwaylights.
Short exposure times are used to avoid
smearing. The position of the lights is
accurately measured in respect to the
runway.
From the position of the lights in the
images  the position of the aircraft can be
calculated. Accuracy up to cm level.
9. Conclusions.
In relatively short time a state of the art
video system was developed.
Using commercial equipment whenever
possible kept costs low, nevertheless
environmental demands have been met.
The system has been used up to now in
flight test practice for two years without
malfunction.
The image processing equipment opens the
possibility for accurate and fast
measurements with video in short time.


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